Earthquake Zones

• About 95% of major earthquakes occur in a few narrow zones

(plate boundaries)

http://www.iris.edu/seismon/

Seismographs (seismometer) - instruments

that record earthquake waves.

Seismograms - traces of amplified,

electronically recorded ground motion

made by seismographs.

Seismograph Seismogram

Types of Waves

#1: P-waves: primary waves

- LONGITUDINAL waves: push (compress) &

pull (expand) in the direction that the

waves travel

- Fastest speed (velocity) of all quake waves

- Travel through solids, liquids & gases

Earthquake Waves

Body Waves – (2 types) P or S waves

#2: S-waves: secondary waves

- TRANSVERSE waves: shake particles

at right angles to the direction that they

travel

- Travel along Earth’s outer layers

- Travel only through solids!!!!!

- Cause more damage than p-waves

Surface waves

- only move across Earth’s surface

- Combination of Earth moving up &

down and back & forth

- Most destruction due to longer

wavelengths

Locating an Earthquake - TRIANGULATION

• Convert the arrival time difference into

distance with a Distance -Time graph

Step 2: Find the Earthquakes Distance

Step 1: Measure the difference in arrival times

between P and S waves from a seismograph

Explaining Earthquakes

• Plot the possible locations

of an earthquake from 3 or

more seismic recordings

TRIANGULATION

Step 3: Find the Earthquakes Direction

Travels the fastest; the first wave to pass seismic stations

Does not travel through Earth’s Body

Waves can only travel through solids

Are push-pull or compression waves

Traverse waves: move particles at right angles compared to the direction that they

travel and are known as

Waves move up and down and side to side

Waves can travel through solids, liquids, or gases

The second wave to arrive a seismic station

The most destructive but are the last waves to arrive at a seismic station

Label the blank areas with one of the three seismic waves